It sold 632,000 copies in the United Kingdom in 2012, the 13th best-selling single of that year.
In the United Kingdom, "Don't You Worry Child" made its debut at number one with first week sales of 135,000 copies. The song was included on their tour One Last Tour, which ended in Miami where they parted ways for five years. The song had its live debut at the Swedish House Mafia's Milton Keynes Bowl concert and its radio debut on Pete Tong's BBC Radio 1 show on 10 August 2012. When it was announced that the tour the Swedish House Mafia was about to set on would be their last, a farewell single was also announced – "Don't You Worry Child" being that single. The title "Don't You Worry Child" was mentioned a few times, with hints from the group members themselves on their Twitter pages. They say it was made from the inspiration they took from the beauty of Australia. The song was announced during the Swedish House Mafia's tour of Australia while they played at Future Music Festival 2012. The song is written in the key of B minor. It was released to massive critical acclaim and received a Grammy nomination for Best Dance Recording in the 2013 Grammy Awards, as did its predecessor, "Save the World", the previous year. It is the group's biggest hit single to date, as well as the final single released before their disbandment in early 2013. In the United States, it is the act's second number-one single on Billboard's Dance/Mix Show Airplay chart, following " Save the World".
It is the last single from their second compilation album, Until Now, featuring vocals from Swedish singer John Martin. " Don't You Worry Child" is the sixth single released by Swedish house music supergroup Swedish House Mafia.